Allthread staging?

So I want to build a MPR to low HPR multistager at some point in the future. My question is this-

Has anyone used allthread rods in conjunction with a stepped thrustplate as a means of staging, rather than a conventional coupler? I'm thinking of something in the LOC 2-3" range with 29 or 38mm, so a coupler would be a pain in terms of fin tabs. This would not be an aggressive project by any means, and is basically just for fun- 3K & mach 0.5 flight profiles for the most part.

The main advantage would be having an almost stock sustainer fin can with only a few holes needed to make it "staging ready". It also seems like the reduced surface area would make drag separation much more likely- there would be less holding the stages together. The rods would be a similar length to a conventional coupler- 3" or so in this case.

Any thoughts?

I don't understand the proposed configuration. Threaded rods are generally used with nuts to hold things together, like holding on a thrust plate, not let them drop away like a separating booster stage. Without nuts they will slip through holes; is it the idea that the rods 1) are attached to the booster and 2) go through holes in the thrust plate attached to the sustainer? Then the rods running in the holes gives you a friction fit to hold the stages together? If so, you'd be much, much better of with smooth rods, not threaded ones, as the threads would act like a file during assembly and separation, and you'd get at most one launch before the holes are worn out.

Assuming that last part is really freakin' obvious, you're probably not proposing that, and I probably just don't get what you're doing.

Fiberglass rods are a better choice.

https://www.google.com/search?q=ROD...rome..69i57.8991j0j7&sourceid=chrome&ie=UTF-8

Info in a couple hyperlinks. Use smooth rods.

Thanks for the advice everyone!

The original idea was:
-Majority of axial load during boost through thrustplate
-Lateral load through allthread
-Allthread fits loosely in sustainer CRs (not friction fit), held together by booster thrust

I was thinking of allthread because of the ease of mounting, but I may just have to go for straight steel and epoxy them in. I would expect abrasion to be less of an issue since the fit will be looser, but maybe it's more of a problem than I think.

Revised version:
Launch lugs inside sustainer fincan
Steel rods epoxied into interstage
Thrust plate on front of interstage
All electronics in the sustainer (booster drag separates at burnout)

Sound doable?

Sent from my LGL44VL using Tapatalk

Personally, I'd use smooth metal rods (can be aluminum, doesn't have to be steel) and thread the ends to mount with nuts while most of the length is smooth. That means buying a die and holder if you don't have one, and good taps amd dies are expensive, but with aluminum rods you only need decent ones. (Never cheap out on crappy ones.) Also, I wouldn't make the holes for a lose fit. If they're not a friction fit they should still be close; you don't want them rattling even a little.

Can you utilize the strength and lightweight characteristics of carbon fiber arrow shafts? You can pick them up at Walmart for cheap!

I started out intending to add in my previous post that epoxying in the rods sounds OK even though I'd be inclined to go a different way. That said:

DRAGON64 said:

Can you utilize the strength and lightweight characteristics of carbon fiber arrow shafts? You can pick them up at Walmart for cheap!

Click to expand...

Ooh, I like, I like. One advantage of threading a rod and using nuts is that you're virtually guaranteed to end up with the rods perpendicular to the centering ring. If using glue (as with the excellent idea above) you might want to devise some sort of jig; I know I would need a jig to keep things aligned just right, but others might be better at this.

Just spitballing here, what if the ISC was just like a regular AV bay with switch band except that the coupler only sticks out the top by 1/4" or so and you have the rods going forward another 2"-3"? It's a little more complicated to glue up, but the small amount of overlap would help keep things centered so you're not depending entirely on the rods. I'd probably glue the rods into the ISC and have them slide freely-but-not-loosely into the sustainer and the booster.

About ten or so years ago a friend of mine named John Smolley showed me a clever minimum diameter staging design that incorporated solid stiff rods (like carbon fiber skewers) that extended from the interstage transition coupler to small tubes set into the fillets of the three fins on the upper stage.